This invention relates to an apparatus for applying padding, especially acoustically active padding, to a component, especially to car body sheet metal.
Pads serving as sound damping layers in the form of bitumen padding are adhered in motor vehicles, for example, against the underside of the vehicle's roof in order to prevent acoustical problems, such as rumbling noises in the motor vehicle. At the present time the acoustically active padding is laid onto a tool body, the latter is shifted with the pad to the correct position under the roof, and then the pad is pressed by hand against the roof through a window created in the tool body. This procedure of hand pressing is very time-consuming and in practice often results in insufficient adhesion of the pad due to insufficient pressing force, so that the pad falls back from the roof with relative frequency. Since the curvature of the vehicle's roof is established with relatively wide tolerances, it has been possible heretofore only with difficulty to automate the procedure of pressing the padding onto it, because in automatic applying devices, dimensional variances of the component to be provided with the pad lead to great differences in the pressing forces.
It is also known in practice to press acoustically active padding against the roof surface by means of a rubber pad to which pressure can be applied. This method of application, however, has the disadvantage that the roof must be given support on the side opposite the pad so that it will not be deformed. Consequently, such kinds of application of padding require relatively great cost in the manufacturing plants.
This invention is addressed to the problem of designing an apparatus of the kind described above such that padding can be applied always with the same uniform contact pressures across the padding in question, to differently curved components made with wide tolerances.
This problem is solved by the invention in that the apparatus has a flexible diaphragm set in a continuous frame for holding the padding on the diaphragm's side remote from the component, that on its front side which faces the component when the apparatus is in use the diaphragm has a circumferential, elastic gasket, and that the apparatus is provided with a vacuum connection for connecting the space between the diaphragm and the component to a vacuum source.
With such an apparatus, even a pad of large area can be applied against an irregularly shaped and less than precisely dimensioned component with a very accurate contact pressure that is uniform across the area of the padding. Since the contact pressure is created by producing a vacuum on the side of the diaphragm facing the component, the occurrence of air spaces is prevented which might result in insufficient adhesion of the padding. In general, the apparatus of the invention is of very simple construction, is of little weight and occupies little space, so that it can be used successfully even where the amount of space available is not great, and its introduction into a car body, for example, by means of a robot, is easily possible. The padding can be acoustically active padding, and also stiffening materials, thermal insulating materials and combination materials. Since the apparatus of the invention operates with a vacuum, the same pressure prevails on the side of the component remote from the padding as prevails on the side of the padding, so that no counter-pressure need be produced. The apparatus of the invention operates instead in a force-neutral manner. It is also suitable for components which have corrugations, for example, because air bubbles are prevented by the vacuum. Another advantage lies in the fact that the pads can be supplied as flat pieces and only with the apparatus of the invention can they be given a shape matching the shape of the component as they are applied.
As is common with acoustically active padding, these pads can be self-adhesive when used with the apparatus of the invention, so that a cover film must be removed before they are adhered. It is also possible, however, to use a pressure-sensitive adhesive or moisture-hardening adhesive, or in the case of a hot-melt glue it can be heated by a heating field and thus activated.
Air inclusions between the component and the film can be prevented especially reliably if, according to an advantageous embodiment of the invention, the diaphragm, when in its state of rest unaffected by the vacuum it is convexly curved toward the component. Thus it can be brought about that, upon its attachment, the pad is first brought in contact with the component in a central area and then applies itself uniformly against the component from the inside out.
It is especially advantageous if, in another embodiment of the invention, the diaphragm in the state of rest lies with its side remote from the component on a support convexly curved toward the component, and the distance from the diaphragm with the pad lying upon it to the top edge of the gasket of the frame is such that the pad does not come in contact with the central surface area of the component until the frame with its gasket is in sealing contact with the component. Such a support makes it possible to adapt to pads of different thickness by using a support with a matching thickness.
If the support consists of a resilient foam substance, the support will be able by elastic deformation to equalize any differences in the component to be provided with the pad.
The apparatus is of especially simple design and permits reliable evacuation if the frame has near its circumferential gasket an annular circumferential passage connected to the vacuum connection, and if a plurality of vacuum orifices distributed over the circumference of the frame lead into the space between the diaphragm and the component.